Dynamic backward seat sliding after impact in a commercial vehicle

ABSTRACT

A safety system for a vehicle seat in a commercial vehicle operating a vehicle seat motion actuation when the commercial vehicle is colliding with an obstacle, comprising: at least one actuator unit that comprises at least one seat actuator to move the vehicle seat from a driving position to a safety position at least one control unit connected to said actuator unit to control the at least one N seat actuator at least one proximity sensor connected to said control unit and configured to detect an obstacle before the commercial vehicle collides it characterized in that the control unit is provided with a calculator device retrieving specific data (Dw, Dw′, Ds, Do) to determine the requested seats motion speed profile and the requested seats motion triggering moment to control, upon receiving an imminent and unavoidable collision alert signal from the proximity sensor, the at least one seat actuator to move the vehicle seat to the safety position.

TECHNICAL FIELD

The invention relates to a safety system operating a vehicle seat motionactuation in a commercial vehicle when the vehicle is colliding with anobject. The invention also relates to a method for actuating a vehicleseat motion in a commercial vehicle when the vehicle is colliding withan object.

The invention is meant to be applied to commercial vehicles such asheavy-duty vehicles, trucks and buses or any vehicles having a distancebetween the front bumper and the driver that is less than 100centimetres.

BACKGROUND

A conventional “pre-crash” passive safety system for vehicles comprisesa series of sensors that can detect an imminent crash, informing an ECU,that will alert driver attention or activate actuators. Said actuatorscan help the driver to prevent impact or prepare to the impact variousaccessories present on vehicle e.g. air-bag, seat belt pre-tensioningdevices . . . .

As it is well known, passive safety systems for vehicles aim reducingconsequences for passengers.

Some known safety devices for vehicle seat are described in applicationWO2011039789. The specific solution proposed in this prior art is onlytargeting the displacement of the back frame and not the whole seat. Theother background presented only applies to passenger cars and not tocommercial vehicles such as trucks.

The solution proposed by applicant in this application is specific tothe trucks configuration which implies technical specificities incomparison to what is proposed for passenger cars due to the very bigdifferences of the crash sequences between a truck and a passenger car.This is mainly due to the fact that the distance between the frontbumper and the driver is dramatically different between a truck and acar: a few dozens of centimetres for a truck and several hundreds ofcentimetres for passenger cars. This structural and geometricaldifference has as a consequence that the time between the impact and thetime when driver's body is enduring the deceleration due to the impactis much shorter for a commercial vehicle such as a truck than for a car.It is therefore considered that solutions proposed that are applicablefor a car are not applicable for a truck due to the time available todisplace the seat in a truck.

Therefore, there is a need for an improved safety system that is able toprepare the seats of a commercial vehicle to act upon the driver andpassenger positions during the very early phases after an impact i.e. ina time slot of about 15 milliseconds.

SUMMARY

An object of the invention is to provide a safety system that wouldenable the driver and passenger seats of a commercial vehicle to havetheir positions adjusted in a few milliseconds just right after theimpact but before the body of the seats' occupants would start todecelerate i.e. within a time window of about 15 milliseconds.

To that end, according to a first aspect, the invention concerns asafety system for a vehicle seat in a commercial vehicle operating avehicle seat motion actuation when the commercial vehicle is collidingwith an obstacle, the safety system comprising:

-   -   at least one actuator unit that comprises at least one seat        actuator to move the vehicle seat from a driving position to a        safety position    -   at least one control unit connected to said actuator unit to        control the at least one seat actuator    -   at least one proximity sensor connected to said control unit and        configured to detect an obstacle before the commercial vehicle        collides it, wherein the control unit is provided with a        calculator device retrieving specific data to determine the        requested seat's motion speed and the requested seat's motion        triggering moment to control, upon receiving an imminent and        unavoidable collision alert signal from the proximity sensor the        at least one seat actuator to move the vehicle seat to the        safety position.

Further, according to the present invention, the safety system's seat'sactuator(s) move(s) the vehicle seat before the seat's occupant bodysuffers the deceleration involved by the collision itself.

In this application we refer to the requested seat's motion triggeringmoment and the requested speed as those two features are calculated andpredetermined by the calculator such that the actuator(s) controls thewhole seat's motion a few milliseconds after the impact but at a momentwhen the deceleration of the vehicle due to the collision has not yetstarted for the seat occupant's body i.e. in a time slot of about 15milliseconds.

Advantageously, the at least one seat actuator moves the vehicle seat tothe safety position in a time frame of thirty milliseconds or less fromthe time the unavoidable collision alert signal is sent from theproximity sensor to the control unit.

The seat adjustment occurring a few milliseconds after the impact butbefore the body starts to decelerate has the benefit to prepare the bodyto the deceleration involved by the impact by creating a firstdeceleration step that will put the body in a better situation towelcome the deceleration involved by the impact itself. This position isreferred to, in this description, as the safety position.

In other words, the seat's occupant body after the first decelerationstep is put into a safer position that will lower the effect of thesecond deceleration avoiding for instance the head tilt. The headtilting thanks to the present invention is realized in a smoother wayduring the controlled first body deceleration step realized by the seatmovement. Further, creating an artificial deceleration in the very earlyphase of the crash allows to start using the safety systems (such assafety belt) earlier and thus with better efficiency.

Advantageously, the safety system of the present invention comprisesfurther sensors such as a sensor measuring the seat occupant's weight, asensor measuring the vehicle speed at the moment of the collision, asensor measuring the collision speed.

According to the present invention, the calculation of the requestedseat's motion speed profile and the right seat's motion triggeringmoment depend at least on the vehicle speed associated with thecollision speed range associated with the seat occupant's weight range.The requested seat's motion speed is calculated such that the seat'soccupant body suffers a controlled pre-deceleration and the requestedseat's motion triggering 25 moment is calculated such that thecontrolled pre-deceleration suffered by the seat's occupant body occursbefore the deceleration involved by the collision itself.

According to a preferred embodiment, the seat motion is a backward seatsliding motion and the safety position corresponds to a specificbackward position of the vehicle seat. It has to be noted that for thepresent invention, when it is referred to a specific backward positionit can be at the end backward position of the usual back stroke of thevehicle seat or only at a portion of it that is sufficient for theseat's occupant to receive a first deceleration e.g. only after the seatmoved backward along two third of the whole back stroke of the vehicleseat. The specific backward position can also correspond to the endbackward position of an additional back stroke (not shown) that wouldhave been built and added on each vehicle seat for the purpose of thepresent invention or it can also correspond to a position at a portionof this additional back stroke.

According to a preferred embodiment, the seat motion is a backward seatsliding motion. Thus, the body of the seat's occupant receives a firstdeceleration step realized by the seat backward sliding in such a waythat it will lower the effect of the second deceleration step, thatsecond one involved by the impact itself.

Furthermore, the solution proposed enables the determination of theright seat motion speed profile. This has the advantage to offer thepossibility to modify the seat deceleration value in order to adapt tothe vehicle speed at the moment of the impact so as to match bothdecelerations (seat and impact decelerations) and keep a manageabledelta of deceleration for the seat's occupant's body between the firstand the second deceleration.

The system may comprise further sensors such as a sensor measuring thevehicle speed at the moment of the collision, a sensor measuring thecollision speed i.e. speed difference between the vehicle speed and thespeed of the object to be collided and a sensor measuring the seat'soccupant's weight. There can also be provided a sensor that identifiesthe type of obstacle to be collided (a vehicle, a wall, a tree etc. . .. ).

The vehicle speed at the moment of the collision is a relevant data ifthe commercial vehicle e.g. a truck is to collide with a fix object(which is not always the case). The collision speed can be calculated bythe proximity sensor that measures in real time the distance between thetruck and the target even if the target is moving. Therefore, thanks tothis sensor, it is possible to calculate the delta speed between thecommercial vehicle and a moving object that is to be collided. The thirddata taken into account is the weight of the driver, necessary to adjustthe power necessary to move the seat at the right speed.

Therefore, the determination of the right seat motion speed profile andthe right triggering moment of the seat's motion according to thepresent invention depend on the vehicle speed associated with thecollision speed range associated with the seat's occupant's weightrange. The system is therefore provided with a calculator device that isable to calculate from the data received by the sensors the right seatmotion speed profile. The calculator device also ideally combines thedata received by the sensors with the vehicle's own data e.g. type ofvehicle, tracted load, and type of cab used, to calculate a moreaccurate requested seat motion speed profile and a more accuratetriggering moment of the seat's motion to provoke the most adaptedpre-deceleration for the seats' occupants' bodies.

As mentioned above, in a preferred embodiment, the vehicle seat motionis a backward seat sliding motion. This backward sliding motion canfurther be combined with other seat motions having several degrees ofliberty or axis i.e. move the seat down on a vertical axis, adjust theback seat position etc. . . . motions that can increase the efficiencyof the body preparation and safety.

According to the present invention, the vehicle seat motion is impartedby an actuator unit that comprises at least one seat actuator that canbe a motor of any type (electrical, pneumatic, pyrotechnic, mechanical,hydraulic, . . . ) but adapted so that power and speed against volumeenable to have an efficient but not a bulky system. The actuator unitalso needs to be able to have the seat prepared and have the full seatmotion undertaken in only a few milliseconds (about 15 ms) so thatmotion of the seat is realised between the moment the imminent andunavoidable collision signal is sent by the proximity sensor and beforethe deceleration from the crash itself is undergone by the driver'sbody.

In a preferred embodiment of the present invention, the proximity sensoris an Advanced Emergency Braking System (AEBS). To improve safety,trucks are now equipped with AEBS, including sensors to collectinformation and a safety electronic control unit to build an alertingsignal for the driver in case of a dangerous traffic situation beingdetected, such as a risk of collision, and to actuate automatically, ifnecessary, an emergency braking to stop or reduce the speed of the truckbefore the collision occurs.

Using the AEBS to trigger the actuation of the seat motion permits tohave a safety system that does not require human intervention to beeffective. Indeed, the seat adjustment occurs therefore at a time thatis so close to the crash that it would have no benefit to try to steerthe vehicle in other directions and braking is already being actuatedautomatically by the AEBS functionality.

Further, using the AEBS to trigger the actuation of the seat motionpermits to have a safety system that does not require human interventionto be effective.

According to a second aspect, the invention concerns a vehicle seatarrangement comprising a passive safety system as previously described.

According to a third aspect, the invention concerns a commercial vehiclecomprising at least one seat provided with the vehicle seat arrangementmentioned above. Further, when the obstacle is a front obstacle and whenthe vehicle is moving forward, the vehicle seat motion triggered by thepassive safety system of the present invention is a backward seatsliding motion.

According to a fourth aspect, the invention concerns a method foractuating a vehicle seat motion when the vehicle is colliding with anobject, the method comprising the following steps:

-   -   the calculator device detects an alert signal that an imminent        and unavoidable collision is about to happen from the proximity        sensor    -   the calculator device retrieves necessary data from various        sensors in the vehicle    -   the calculator device combines the retrieved data with the        vehicle's own data    -   the calculator device calculates the requested seat motion's        speed and the requested motion's triggering moment    -   the calculator device sends a signal to the seat actuators so        that they prepare to move the seat with the requested force and        are able to move the seat(s) at the predetermined calculated        (i.e. requested) speed to ensure a controlled pre-deceleration        of the body of the seat's occupant.    -   The calculator device calculates the moment of the intended        unavoidable impact and sends at that calculated moment a        triggering signal to the actuator unit of the actuator so that        the whole seat motion is started at the requested moment such        that the controlled pre-deceleration suffered by the seat's        occupant body occurs before it undergoes the deceleration        involved by the collision itself.

According to the present invention, the vehicle seat is moved to thesafety position in a time frame of thirty milliseconds or less from thetime the unavoidable collision alert signal is sent from the proximitysensor to the control unit.

Therefore according to the present invention, the whole seat motion isstarted at the exact timing to enable the whole seat being movedbackward right after the impact but at a moment when the deceleration ofthe vehicle due to the collision has not yet started for the seatoccupant's body.

Further advantages and advantageous features of the invention aredisclosed in the following description and in the dependent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

With reference to the appended drawings, below follows a more detaileddescription of embodiments of the invention cited as examples.

In the drawings:

FIG. 1a to 1d are schematic representations from the side of the seatand its occupant at different moment during the 15 milliseconds inbetween the impact and the deceleration due to the impact.

FIG. 2 is a picture showing the different AEBS phases and for each phasethere is shown the human machine interface signals sent to the driver,the vehicle speed and the vehicle retardation (i.e. the slowdown of abody movement when this slowdown is the effect of a particular cause).

FIG. 3 is a flowchart showing a sequence of operations for the safetydevice to actuate the vehicle seat motion according to the presentinvention.

FIG. 4 is a schematic top view of the interior of a vehicle's cabprovided with a safety system according to one possible embodiment ofthe present invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS OF THE INVENTION

Reference to FIG. 4 is made all along the following description incombination with the other figures.

FIGS. 1a to 1d are schematic representations from the side of the seatand its occupant at different moments during the 15 milliseconds inbetween the impact and the deceleration due to the impact.

FIG. 1a shows the seat occupant before the impact.

For the ease of the understanding we will use “driver” to designate theseat's occupant but it has to be understood that it could also be apassenger sitting on a seat provided with the device of the presentinvention.

In FIG. 1 a, seat 2 and driver 1 are in a normal driving position.

The driver 1 is seated in his vehicle seat 2 with his back resting onthe back seat 3 that is inclined according to the driver's preferenceswhen driving. The sitting portion 4 of the seat 2 that receives thebuttocks and upper thighs 5 of the driver 1 is almost parallel to theground floor 6 of the vehicle's cab. The head 7 and neck 8 of the driver1 are in a perfect driving position i.e. aligned along an axis HH' thatis almost perpendicular to the ground floor 6 of the vehicle's cab.

This position is the same as the one a few milliseconds before theimpact except that a few milliseconds before the impact the seat'sactuators 16 (see FIG. 4) are warned by the proximity sensor 11 that acrash is imminent. At that time, the actuators 16 are getting preparedfor a quick backward movement but the seat 2 is not yet moving backwardin order to let the driver 1 a full control of the vehicle 20 for thelongest possible period of time and the ability to use the steeringwheel 19 in order to avoid the obstacle for instance.

The seat motion actuators may be for example, electrical actuators whereelectrical motors will rotate a threaded screw on which the seat isfixed in order to make the seat moving backward. Another type ofactuators that can be envisaged for the present invention are pneumaticactuators using a cylinder with a piston equipped with a pressurizedchamber in which a high pressure is constantly applied. This highpressure can be released into the piston chamber via a controlled valvemaking the piston on which the seat is fixed moving quickly along alongitudinal axis (i.e. along the longitudinal direction of the vehicle,in a backwards direction). Another type of actuators to be consideredare the pyrotechnic actuators which are similar to the pneumaticactuators except that the piston movement is actuated by an explosioninvolving a gas dissipation creating a high pressure in the pistonchamber ending in the piston on which the seat is fixed move along alongitudinal axis i.e. making the seat move along a longitudinal axis ofthe vehicle i.e. in a backwards direction. Finally, mechanical actuatorscould also be used.

These ones using a compressed spring that is released via a controlledactuator to push an axle on which the seat is fixed could also enable aquick motion of the seat in a backwards direction.

FIG. 1b shows the driver 1 in driving position at the exact moment ofthe impact. In this figure, it is clearly shown that, at that exactmoment of the impact, the body is not experiencing any deceleration. Theposition is identical to the one of FIG. 1a but the seat 2 is fullyready to start the backward movement. At this time it is useless tostill give the possibility for the driver 1 to control the vehicle asthe crash has started. The distance between the seat 2 and the dashboard9 is shown with reference 10, the inclination of the back seat 3 betweenin the normal driving position and the moment of the impact is shownwith reference 11.

FIG. 1c shows the driver position a few milliseconds after the impact.At that moment, the vehicle's cab is decelerating but the driver's bodyis not yet experiencing any deleration caused by the cab. The seat 2 ismoving backward (distance 10 is increased) and seats metrics areadjusted to put the driver's body into a position which is adequate tobest prepare the driver's body to receive the deceleration due to theimpact. The whole seat 2 is suddenly moved backward and the motion ofthe sitting portion 4 of the seat 2 provokes automatically a tilting ofthe backrest portion 3 of the seat 2. The backrest portion 3 is afterthe pre-deceleration almost perpendicular to the ground floor 6 of thevehicle's cab (the inclination of the back seat 3 between in the drivingposition and a few milliseconds after the impact is shown with reference11). This fast backward movement combined with the seat's new positionalso provokes a controlled head tilt (the head and neck are no longeraligned along the axis HH′ that is almost perpendicular to the groundfloor 6 of the vehicle's cab). An advantage is that the head tiltprovoked by the seat movement is much smoother and controlled than if ithad been provoked by the crash deceleration itself. FIG. 1c furthershows that, after the pre-deceleration, the head has indeed been movedforward and is above the high thighs 5 of the driver 1 nearer to thedashboard 9 and hence to the steering wheel 19 in a position such thatwhen the airbag will deploy there will be no violent head tilting. Thelower part of the back of the driver 1 is not resting on the back seatportion 3 of the seat 2 anymore. This pre-deceleration puts thereforethe driver into a “deceleration position preparation” that will lowerthe effect of the much more violent deceleration caused by the effect ofthe deceleration of the impact itself. Additionally, pre-tensioners 18are actuated to re-enforce a controlled pre-deceleration.

Advantageously, the intensity of the pre-deceleration can be adjusted soas to match in a better way the second stronger deceleration. In factthe intensity of the deceleration has the effect to have the whole bodyof the driver 1 put in a shock condition with for instance musclescontracted that has the effect of lowering the harm done to the body bythe deceleration due to the impact itself. Therefore in FIG. 1 c, thedriver 1 is in an optimum position and his body is in the optimum stateto endure a deceleration. This is clearly shown in FIG. 1d . Indeed, thebody is already decelerating thanks to the seat motion lowering thebrutal effect of the deceleration of the cab due to the impact. As canbe seen in this figure, due to the deceleration of the cab, the seat 2is brutally brought forward and airbag 21 is deployed. Thanks to the premotion of the seat 2 there is no extreme violent seat tilting and henceno violent head tilting.

FIG. 2 is a picture showing the different AEBS phases and for each phasethere is shown the human machine interface signals, the vehicle speedand the vehicle retardation.

As mentioned above, in a preferred embodiment of the present invention,the proximity sensor 11 is an Advanced Emergency Braking System (AEBS).

There are three main AEBS phases.

The first phase is initiated when cameras and radars installed on thefront part of the truck detect that a collision has a very highprobability to happen i.e above 90% risks of a collision to happen sothere is still a slight chance to avoid the collision if the driverreacts properly e.g. a steering wheel movement. This first phase istriggering audio and visual alerts to warn the driver that he has to actin order to avoid the collision.

The second phase is initiated when cameras and radars installed on thefront part of the truck still detect that the collision has a very highprobability to happen meaning that the driver did not take any action toavoid the collision. This second phase does not require a full brakingperformance, even if it is already applying a strong braking request.This second phase is to lower the vehicle speed (e.g. stop theacceleration and start to slow down the vehicle) and mainly to warn thedriver in addition to other audible and visual alerts set preliminary inthe first phase.

The third phase is initiated when the collision is imminent e.g. willhappen in less than one second, and that the driver did not take anyaction after phase 1 and 2 (alerts and pre brake) or that the actionundertaken by the driver will not suffice to avoid the collision. Thisthird phase requests the maximum braking possibility of the vehicleconsidering that entering that third phase means an unavoidablecollision.

By using the AEBS as a proximity sensor 11 for the safety system of thepresent 35 invention, this enables to inform the driver and passengerseats 2, 2′ prior to a maximum braking performance request. Indeed, theAEBS system usually comprises at least a radar combined with a camera,and can detect an obstacle located at a quite long distance such a fewdozens of meters. Therefore, the system can track the object in advanceand build a collision's imminence information along the timeaccumulating data. As long as the object is detected, the system canmonitor the delta speed between the truck itself and the object upfront.Knowing the dynamics parameters of the truck (weight, brakingpossibilities depending on the weight etc. . . . ) the system can becalibrated to determine when a collision becomes unavoidable. Acollision is therefore considered unavoidable using a combination ofinformation by the AEBS system such as:

-   -   the obstacle speed    -   the vehicle speed    -   the difference between the obstacle speed and the vehicle speed    -   the vehicle's breaking possibilities depending on the weight of        the vehicle    -   the vehicle's breaking possibilities based on the road        conditions (temperature, rain and/or ice on the road)    -   the steering wheel angle    -   the possible trajectory of the vehicle at each steering wheel        angle

All these information can be used by the system to determine a certainpoint in time when the collision cannot be avoided even if the driverwill finally turn the steering wheel or if the driver already turns it.The system is therefore able to adjust the alert timing and the brakingtiming. Combining the safety system of the present invention to such anAEBS offers the possibility to prepare the seat movement when thecollision is imminent but only trigger and engage the seat(s) motionwhen the collision is unavoidable.

Advantageously, the AEBS may comprise further sensors to further helpobstacle's detection such as ultrasonic sensors (short range), radars(Miliwaves and Microwaves), lidars, cameras . . . .

The driver and passenger seats 2, 2′ will therefore have their positionsadjusted thanks to the fact that seat motion actuators 16 have receivedthe information up front, offering the possibility for the seats to getprepared for a quick adjustment just before the impact as detailed abovewith FIGS. 1a to 1 c.

The additional advantage of the present invention is that knowing thecollision is imminent and the AEBS system being able to determine acertain point in time when the collision cannot be avoided, it istherefore possible to actuate the seat motion at the requested momentand with the requested speed profile so that the body of the driver 1receives a first deceleration before it undergoes the deceleration forcedue to the impact.

Further, it enables to put the body of the driver 1 in the safestpossible position to endure a crash without requesting an interventionfrom the driver 1 i.e. if the driver 1 is unconscious, the system willstill be able to position the driver's body in the safety position,better prepared to undergo a crash.

FIG. 3 is a flowchart showing a sequence of operations for the safetydevice to actuate the vehicle seat motion according to the presentinvention and FIG. 4 is a schematic top view of the interior of avehicle's cab provided with a safety system according to one possibleembodiment of the present invention. In the following part of thedescription we will discuss both figures simultaneously.

As mentioned earlier the vehicle 20 is provided with several types ofsensors 11, 12, 13, 14 that could be integrated in devices such as acamera or a radar. These sensors 11, 12, 13, 14 collect data that aresent to a specific ECU 15 referred to as a calculator device that isable using many collected data to calculate the right seat motion speedprofile and the right moment to trigger the seat motion so that thesystem enables to position the driver in the safest possible position toundergo a crash, the intensity of the pre-deceleration being adjusted soas to match in a better way the second stronger deceleration.

Once the calculator device 15 has processed the data available, it sendsa signal S1 to the seat's actuators 16 using any type of communicationmeans such as a software communication line (BUS) or a hardwarecommunication line (electric impulsions via a wire) or even a wirelesscommunication means.

Once the actuators 16 that are provided with an actuator unit 17 havereceived the signal S1, they get prepared for a quick motion of theseat(s) 2, 2′ at the right force i.e. so that the motion of the seat(s)2, 2′occurs at the right speed as calculated by the calculator device15. The calculator device 15 also calculates the right moment to triggerthe seat's motion i.e. the calculator 15 is able to calculate, dependingon several factors as already mentioned, the moment of the intendedunavoidable impact and sends a second signal S2 to the actuator unit(s)17 of the actuator(s) 16 to trigger the motion of the seat(s) 2, 2′ atthat calculated moment such that the motion of the seat(s) 2, 2′ startsright after the crash but at a moment when the deceleration of thevehicle 20 due to the collision has not yet started for the seatoccupant's body.

Therefore, the sequence of operations for the safety device to actuatethe vehicle seat motion according to the present invention can be:

-   -   The proximity sensor 11 detects an imminent and unavoidable        collision and sends an alert Al that is detected by the        calculator device 15    -   The calculator device 15 retrieves necessary data Dv, Do, Dw,        Dw′ from various sensors 12, 13, 14, 14′ in the vehicle i.e.        speed sensor, seat's weight sensors, type of obstacles sensor        etc. . . .    -   The calculator device 15 combines the retrieved data Dv, Do, Dw,        Dw′ with the vehicle's own data i.e. vehicle type, cab type,        tracted load that are either calculated by other ECUs of the        vehicle or stored in the vehicle's main ECU's memory and sent to        the calculator 15 using any type of communication means such as        a software communication line (BUS) or a hardware communication        line (electric impulsions via a wire) or even a wireless        communication means    -   The calculator device 15 calculates the right seat motion's        speed and sends a signal S1 to the seat actuators 16 so that        they prepare to move the seat with the right force and are able        to move the seat(s) 2, 2′ at the right calculated speed to        ensure a controlled pre-deceleration of the body of the seat's        occupant    -   The calculator device 15 also calculates the moment of the        intended unavoidable impact and sends at that calculated moment        a triggering signal S2 to the actuator unit(s) 17 of the        actuators 16 so that the whole seat motion is started at the        right moment to enable the whole seat being moved backward right        after the crash but at a moment when the deceleration of the        vehicle due to the collision has not yet started for the seat        occupant's body    -   At that moment, the calculator device 15 may also actuate the        seat belt pretensioners 18 to reinforce a controlled        pre-deceleration and decrease the risk of injury to the driver's        thorax.

It is to be understood that the present invention is not limited to theembodiments described above and illustrated in the drawings; rather, theskilled person will recognize that many changes and modifications may bemade within the scope of the appended claims.

1. A safety system for a vehicle seat in a commercial vehicle operatinga vehicle seat motion actuation when the commercial vehicle is collidingwith an obstacle, comprising: at least one actuator unit that comprisesat least one seat actuator to move the vehicle seat from a drivingposition to a safety position; at least one control unit connected tothe at least one actuator unit to control the at least one seatactuator; and at least one proximity sensor connected to the at leastone control unit and configured to detect an obstacle before thecommercial vehicle collides; wherein the at least one control unit isprovided with a calculator device retrieving specific data to determinea motion speed profile and a motion triggering moment to control, uponreceiving an imminent and unavoidable collision alert signal from theproximity sensor, the at least one seat actuator to move the vehicleseat to the safety position.
 2. The safety system of claim 1 wherein theat least one seat actuator moves the vehicle seat before an occupantbody suffers the deceleration involved by the collision itself.
 3. Thesafety system of claim 1 wherein the system comprises further sensorssuch as a sensor measuring a weight of an occupant of the vehicle seat,a sensor measuring the vehicle speed at the moment of the collision, anda sensor measuring the collision speed.
 4. The safety system of claim 2wherein the calculation of the motion speed profile and the motiontriggering moment depend at least on the vehicle speed associated withthe collision speed range associated with the seat occupant's weightrange.
 5. The safety system of claim 1 wherein the motion speed profileis calculated such that an occupant suffers a controlledpre-deceleration and the motion triggering moment is calculated suchthat the controlled pre-deceleration suffered by the occupant occursbefore the deceleration involved by the collision itself.
 6. The safetysystem of claim 1 wherein the at least one seat actuator moves thevehicle seat to the safety position in a time frame of thirtymilliseconds or less from the time the unavoidable collision alertsignal is sent from the proximity sensor to the at least one controlunit.
 7. The safety system of claim 1 wherein the safety positioncorresponds to a specific backward position of the vehicle seat
 8. Thesafety system of claim 1 wherein the at least one seat actuator is amotor that is an electric, a pneumatic, a pyrotechnic, a hydraulic or amechanic motor.
 9. The safety system of claim 1 wherein the proximitysensor is an Advanced Emergency Braking System.
 10. (canceled)
 11. Thesafety system of claim 1 wherein the backward seat sliding motion iscombined with other seat movements to adjust metrics of the vehicleseat.
 12. (canceled)
 13. (canceled)
 14. A method for actuating a vehicleseat motion in a vehicle provided with a passive safety system,comprising: detecting, by a calculator device, an alert signal that animminent and unavoidable collision is about to happen from a proximitysensor connected to at least one control unit of a vehicle; retrieving,by the calculator device, necessary data from various sensors in thevehicle to combine retrieved data with vehicle data; calculating amotion speed profile and a motion triggering moment; sending, by thecalculator device, a signal to an actuator to be prepared to move theseat with a force and at a calculated speed to ensure a controlledpre-deceleration of an occupant of the vehicle seat; and sending, by thecalculator device, a triggering signal at the calculated moment of theintended unavoidable impact to the actuator unit so that a whole seatmotion is started at the calculated moment such that a controlledpre-deceleration suffered by the occupant occurs before the decelerationinvolved by the collision itself.
 15. The method of claim 14 wherein thevehicle seat is moved to a safety position in a time frame of thirtymilliseconds or less from the time the unavoidable collision alertsignal is sent from the proximity sensor to the at least one controlunit.